Microarray-based bioinformatics analysis of osteoblasts on TiO2 nanotube layers

The TiO2 nanotube layers fabricated by electrochemical anodization have received considerable attention in dentistry and orthopedic medicine due to their increased osseointegration compared with the unanodized titanium. The molecular mechanisms underlying the interactions between nanotubes and osteoblasts is unknown. To examine this, the mRNA expression profile of MG-63 osteoblast-like cells cultured on the TiO2 nanotubes was explored by DNA microarray. The differentially expressed genes were identified by bioinformatics analysis. Gene ontology (GO) and Go-map network analysis indicated that the TiO2 nanotubes enhanced osteoblast proliferation and differentiation and decreased osteoblast adhesion and immunization. The expressions of genes were mainly increased in pathways influencing cell proliferation and differentiation (Cell cycle, Terpenoid backbone biosynthesis, and TGF-beta signaling) and were decreased in pathways controlling cell immunization (Cell adhesion molecules (CAMs), Allograft rejection, and Graft-versus-host disease). Signal network analysis generated from differentially expressed genes suggested that CTNNB1 (beta-catenin) was the central gene for increasing osteoblast proliferation and differentiation, and IKBKG (inhibitor of kappa light polypeptide gene enhancer in B-cells, kinase gamma) was the central gene for repressing osteoblast immunization on nanotube layers. These two genes were further confirmed by quantitative PCR. The identified signal pathways and central genes in the study are well correlated with osteoblast phenotype. Furthermore, microarray-based bioinformatics analysis is a powerful tool in efficiently understanding molecular mechanisms underlying the interactions between osteoblasts and the nanotube layers.